Touch sensitive screen can be used to provide text input, and other commands such as for scrolling and zooming functions. Panning in a horizontal or a vertical direction can be done by moving a finger or some kind of stylus or pen in a horizontal (X-axis) and/or vertical direction (Y-axis). Zooming can be done by multi-touch finger pinching and then moving the fingers outwards or inwards while the fingers are still in contact with the touch screen. However, each time a user wants to transition from one command to another, some existing systems require the user to lift their fingers and again put them in contact with the touch-screen. The action of lifting the fingers indicates to the system the termination of a current command (e.g., the end of a pan command, the end of a zoom command, etc.).
In natural user interface systems where the display screen is at a distance from the user, user input is provided based on gestures. In such systems, detection of an activation movement (e.g., moving a hand from right to left) locks the user into a particular command, and ignores additional user movements (e.g., up and down) unless the user terminates the currently movement with an explicit release or termination gesture (e.g., putting the hand to a side of the user). Thus, the existing systems recognize individual, discrete gesture inputs corresponding to commands, but only with explicit release gestures inbetween each of the commands.